What’s eating our evergreen trees?

The balsam fir, a tree now starring in many homes as the centerpiece of Christmas decorations, has a tiny enemy in the wild. So does the hemlock, the Pennsylvania state tree.

Balsam Woolly Adelgid

Their nemesis is a little sucker, literally: an insect called the woolly adelgid.

“It has a piercing, sucking mouthpart almost like a straw, and it puts that straw into the tree’s bark and sucks out the juices,” explains Jason Lubar, Associate Director of Urban Forestry at the University of Pennsylvania’s Morris Arboretum.

You can do something to help these evergreens survive. A group of scientists called the Alliance for Saving Threatened Forests is enlisting volunteer tree spotters. The goal is to identify hemlocks and balsam firs that are healthy, even though surrounding trees are succumbing to the woolly adelgids.

“We’re hoping we can find some natural resistance within our native population,” notes Fred Hain, a forest entomologist with the Alliance. “We’re interested in breeding trees that have resistance to exotic forest pests. So we’re looking for trees that are still alive, look relatively healthy, they may be infested or they may not be infested. But as long as they look fairly healthy, with good crown color, and a fairly dense crown, that suggests to us that they may in fact be resistant.”

So that’s the job for citizen scientists willing to tromp through the woods: spot a healthy tree, record its location, and register it on the project website. More on how to do that in a bit.